Geosynthetic reinforced segmental retaining walls

Segmental retaining walls (SRWs) (primarily those with precast concrete block facing) reinforced by geogrids or geotextiles are in a period of enormous growth. Estimates are that 35,000 of these walls exist and that they cover the entire range of practical wall heights. This paper gives a perspective of the evolution of retaining walls in general, and follows with results of a recent cost survey. It is seen that geosynthetic reinforced walls are the least expensive of all wall categories and at all wall heights. Three design methods are then compared to one another with respect to their details and idiosyncrasies. This is followed by a numeric example showing that the modified Rankine method is the most conservative, the FHWA method is intermediate, and the NCMA method is the least conservative. A survey of the literature is included where it is seen that there have been approximately 26 walls which suffered either excessive deformation or actual collapse. The overwhelming causes for these cases of poor performance were (i) backfilling with improperly draining fine grained soil and (ii) contractors deficiencies which could have been avoided with proper quality control and inspection. The paper. which reflects North American practice, closes with a discussion of possible concerns most of which are under active investigation. Clearly, continued strong growth for geosynthetic reinforced SRWs is justified. (C) 2001 Elsevier Science Ltd. All rights reserved.